In certain image capture systems it is often desirable to suppress (a) blurriness of individual pictures, (b) undesired displacements of individual image sequence frames or (c) unevenness of an image motion path during panning. This applies particularly to hand-held image capture systems that capture a sequence of images, for example film cameras and binoculars.
The prior art has various solutions that are known. For film shots, tripods are often used, since to date only these satisfy professional requirements for blur-free images. The disadvantage of tripods lies in their size and weight. Therefore stabilization systems have been incorporated into image capture systems, particularly binoculars and video cameras.
There are therefore stabilization systems integrated within image capture systems, or placed thereon, wherein controllable optical elements shift the image projected to the focal plane. Mirrors, variable prisms or lenses, which can move laterally to the optical axis, are for example employed as controllable optical elements. Their displacement is controlled by a movement sensor such that image shifts caused by trembling of the image capture system is compensated. Such systems have the advantage that they can also be used for film cameras, which record on chemical film.
In addition, for image capture systems with electronic capture sensors, such as video cameras for example, there are image stabilization systems which select the image section to be utilized. This image section (and/or capture sensor) is shifted by a movement sensor such that image shifts caused by trembling of the image capture system are followed as exactly as possible in the sensor plane.
These optical and electronic stabilization systems essentially work on the same control principle. A desired target alignment or target alignment sequence of the image capture system and thus a desired image section or image section sequence is compared with the real particular actual alignment of the image capture system, and an alignment difference is determined thereby. Solutions of the most varied kind, which for example use acceleration sensors, gyroscopic systems, angular measuring devices, etc., are already known for technically executing such determination of the alignment difference. Any deviation from the desired image detail caused by a particular alignment difference is compensated by one of the compensation devices described above.
Both optical and electronic stabilization systems operate to suppress undesired high frequency alignment differences according to this control arrangement. However they do not account for low-frequency alignment differences which are caused particularly by a user through his unavoidable, slow swaying movements, whenever for example he is holding a film camera or binoculars by hand. These slow movements cannot be compensated, at least above a certain limit, since otherwise it would not be possible to carry out image section displacements during an intended panning movement of the image capture system. Conventional stabilization systems do not have the facility of clearly differentiating whether a slow movement of the image capture system beyond a certain limit is undesired or intended.
None of the systems known to date can meet all requirements of an ideal stabilization system. A tripod only results in perfectly blur-free image detail with a stable base, whereas perfect, even panning can only be achieved with great difficulty, since the panning speed in practice depends on the amount of pressure on the panning lever and whereas the operator gets no feedback as to whether he possibly is exceeding the allowable maximum panning speed. The known optical and electronic stabilization systems suppress undesired high-frequency trembling, but they cannot achieve a completely motionless and blur-free image sequence or stabilization of a motion path, which for example is necessary in the case of horizontal panning.